For those looking for a clearer standard it's the International Terrestrial Reference System and Frame [0]. The better datums in use today are tied to a particular year (epoch) reference frame of this.
For instance Australia's GDA2020 [1] is based on ITRF2014 at epoch 2020.0. It replaced GDA94 which was based on ITRF1992 at epoch 1994.0. The difference is around 1.8 metres